Portable belt sander



Oct. 28, 1941. A w, MALL POR'FMBLEl BELT SANDER Filed Juney 9, 1939 2 sheets-sheet 1 :E L Fa lcilll Oct. Z8, 1941.

A. W. MALL PORTABLE BELT SANDER Filed June 9, 1939 2 Sheets-Sheet 2 l g3 501D j@ 56 5.9

2f jd 2j ZI, v

Patented Oct. 28, 1941 PORTABLE BELT SANDER Arthur William Mammossmoor, nl.

Application June 9, 1939, serial No. 278,293

(ci. 511'zo) s'claims.

This invention relates to portable belt type motor driven sanding machines, and has as itsv the sanding belt travels, so arranged that the roller may be easily adjusted while the belt is in tension. In prior structures, the adjusting of the roller in one direction tends to tighten the belt, and, in the other direction, to loosen the belt. My invention provides an arrangement wherein the belt tension will remain constant during the adjustment, and will not oppose the adjusting movement.

Another object of the invention is to provide a sander of the type specified, equipped with a readily detachable suction unit. The invention aims in this respect to provide an v'arrangement such as to reduce to a minimum the expense of making a change from a non-suction to a suction type machine. To this end, the suction fan is mounted in a detachable fan housing and nozzle unit, in individual bearings on a shaft which is separate from but adapted to be coupled to the.

shaft of the driving motor of the machine, when the suction unit is attached.

Another object of the invention is to provide a portable sanding machine of the type mentioned, in which one of the belt carrying rollers is mounted for retracting movement to permit easy removal and replacement of the sanding belt. In this respect the invention provides a quick-acting means for securing the roller in a retracted, belt releasing position, against the pressure of a spring which normally holds the roller in extended, belt tightening position under a predetermined tension.

Other objects, the advantages and uses of the invention will becomeapparent after reading theA following specications and claims, and after consideration of the drawings forming av part of the specification, wherein:

roller carriage vand operating means therefor, taken on the line 4-4 of Fig. 1; and

Fig. 5 is a detail sectional view of the front f roller carriage, taken on the line 5-5 of Fig. 2.

As an illustration of one form in which the invention may be embodied, I have shown in the accompanying drawings a portable belt sanding machine comprising, in general, a sanding belt and belt mounting roller assembly A, an electric motor B for driving the same, gearing C for transmitting power from the motor B to the belt A, and a suction unit D for removing the dust particles produced in a sanding operation.

The motor B comprises a domed housing I0' encasing a conventional field coil II and armature I2, the latter mounted on a shaft I3 one end oi!v which'is mounted in a bearing I4 in the domed end of the housing.

Formed integrally with the underside of the housing I0, on one side thereof, is a downwardly projecting bracket I5, which projects laterally beneath the upper reach of the belt I3, to form a guide cylinder I1 for the roller carriage I8, and projecting beyond the cylinder I1', a bed I9 to which is secured, as by screws 2li, a shoe 2l against which the lower reach of the belt I3 travels. The shoe 2l is provided with a polished lower surface the major portion of which lies below the plane of the lower extremities of the rollers 22 and 23, and the end regions of which are inclined at a tangent to the rollers.

The bracket I5 is extended forwardly to form a hood 24 extending over the front roller 22.

The gearing unit C includes a gear case 25 secured to the rear end of the motor housing I0, and having at one side a vertically extending belt housing 26 which projects below the gear case 25 to form a roller bracket 21. Formed integrally with the bracket 21 is a boss 2,8 which projects laterally between the'reaches of the belt I6. In the boss 28 are mounted roller bearings 28 and 30, in which the shaft 3I of the rear roller 23 is journalled. The rollers 23 may be secured on the shaft 3| by a nut 32 threaded onthe end of the shaft and engaging the hub of the roller. The rear end of the motor shaft I3 is journalled in bearings 33 and 34 mounted in a worm casing 35 formed in the center of the gear housing 25.

Between the bearings 33 and 34, in the worm casing 35, on the shaft I3, is a worm 36, which meshes with a worm wheel 31 secured on a shaft 38 which is journalled in bearings 39 and 40 in a boss 4I joining the lower region of the worm asiisg 35 and the upper region of the b elt hous- -recess 48 in the forward end of the cylinder,

defining a 'pair of guide fingers 41 between the fiat inner faces of which 'the head 45 is restrained frommuon but allowed to slide axially.

The head 45 is extended forwardly and received between furcations 48 formed on the rear end of an arm 49 on which the front roller 22 is mounted. A pin 50 extends throughthe furcations 48 and head 45 to form a pivotal connection between the roller arm and the car- -riage I8.

The front roller 22 is in the form of two axially separated roller sections, mounted on the respective ends of a shaft I which is journalled in bearings 52 mounted in a sleeve 53 formed on the forward end of the arm 49. The arm 49 extends between the rollex` sections as shown, and is made fairly thin horizontally so that the roller sections maybe spaced fairly close together.

Formed on the arm 49 and projecting laterally from the furcations 48, is an ear 54. Formed on the head 45 and extending substantially parallel to the ear 54, is an ear 55. An adjusting screw 58 is extended through the ear 55'and threaded into the ear 54," It serves to draw the ears toward each other and thereby to swing the arm 49 clockwise as viewed in Fig. 2. A compression spring 51, interposed between the ears 54 and 55 and encircling the screw 55, serves to spread the ears when the screw is unthreaded, and thereby causes the arm 49 to swing counterclockwise 'as viewed in Fig. 2. Thus the roller axis may be adjusted to parallelism with the axis of the rear roller so as to cause the belt to run true.

During such adjustment, the pull of the belt will be balanced on either side of the pivot 50, thus making the adjustment a relatively easy one to perform.

The carriage I8 is urged forwardly by a compression spring 58 extending into a bore 59 in its rear end and engaged between the end of the bore 59 and the end of the cylinder I1. The pressure of the spring 58 determines the tension of the sanding belt I6.

The carriage I8 is retracted by means of an eccentric 60 including a trunnion 6I journalled in a bearing 82 projecting laterally from the cylinder I1, having at one end an eccentric pin 83 extending into a vertical slot 64 in the side of the plunger 43. At its other end, the trunnion 5I is formed withV astub shaft 65 projecting through a retaining flange 66 secured as at 61 to the end of the bearing 82 and retaining the trunnion therein. A lever 68 is lsecured to the projecting end of the stub shaft 65 and, when oscillated counterclockwise to the position indicated in dotted lines in Fig. l, is adapted to oscillate the trunnion 6I so as to move the eccentric pin 63 rearwardly and downwardly. The pin 83, in this moving, will engage the rear side of the slot 64, push the plunger rearwardly to the belt releasing position, and, just before the lever .58 contacts the bed I9, will pass dead center so as to lock the carriage in the retracted position until it is manually released therefrom, Such release is accomplished by lifting the lever until the pin 63 passes above dead center, whereupon the carriage will advance to the belt tightening position under the urge of the spring 58.

This arrangement greatly facilitates belt changing.

The suction unit comprises a fan casing 69 detachably secured to the gear housing 25 as by screws 10 extending through bosses 1I in the casing 59 andthreaded into the housing 25. The front wall of the fan casing 69 may comprise a detachable plate 12. In bearings/ 13 mounted on the front and rear walls of tlie fan casing.

is a fan shaft 14 on which is mounted a fan im peller'15 of the open-bladed type. The fan is adaptedto draw dust laden air through the inlet 16 of the fan casing from a suction nozzle 11 which forms a downwardly extending continuation of the fan ,casing 69, and to discharge such air through the fan outlet 18 into a suitable filtering receptacle (not shown) attached thereto.

The fan shaft 14 has at its forward end a flat clutch finger 19 projecting forwardly into a clutch slot in the end of the'motor shaft I3, thus coupling the fan shaft to the motor shaft to be driven thereby.

This construction makes it possible to 'uickly detach the suction unit without disturbing the motor shaft. In previous devices of this kind, it has been necessary to remove the entire motor armature in detaching the suction unit.

At the forward end of the machine, attached to the motor housing III, is a handle 8| of conventional design. The suction unit carries a conventional rear handle unit 82 of the pistol grip type embodying a switch operating trigger 83 for controlling the operation of the motor A. When it is desired to provide the machine without the suction unit, a similar handle, minus the suction unit, may be supplied for attachment in the same manner as the suction unit.

I claim:

1. In a portable belt sander,- a frame, a pair ,of spaced rollers carried by said frame, a sanding belt trained about said rollers, a motor carried by the frame above the upper reach of said belt, a shaft projecting rearwardly from said motor. a gear housing having a portion above said upper reach, through which said shaft extends, and a suction unit comprising a fan casing detachably secured to the rear of said gear housing, and having a suction nozzle projecting downwardly behind the rear roller, and a fan rotatably supported in said fan casing, for removal therewith, said fan being provided with separable coupling means adapted to establish driving engagement with said motor shaft when the fan casing is attached to the gear housing.

2. In a portable belt sander, a frame, a pair of spaced rollers journalled on said frame, a sanding belt extending around said rollers, a motor carried by the frame above the upper reach of said belt, a shaft projecting rearwardly from said motor, a gear `-housing having a portion above said upper reach, through which said shaft extends, and a suction unit comprising a fan casing secured to the rear of said gear housing and having -a suctionl nozzle projecting downwardly behind the rear roller, a fan shaft in said fan casing, bearings mounted in said fan casing in which said fan shaft is journalled, the forward end of said fan shaft having a projecting coupling said motor shaft .to the Ian, and gearing in the gear housing, connecting said motor shaft to said rear roller.

3. In a portable belt sander, a frame, a pair of spaced rollers carried by the frame, a sanding belt trained about the rollers, a motor carried by the frame above the upper reach of said belt, a shaft projecting rearwardly from the motor, a. gear chamber, and a suction unit detachably mounted at the rear of the gear chamber, a. wail region between the suction unit and gear 'chamber adapted to prevent dust from getting into the gear chamber, said suction unit having a dust collecting chamber and a fan rotatably supported in said chamber, for removal with the suction unit, said fan being provided with separable coupling means adapted to establish driving engagement with said motor shaft when the suction unit is attached at the rear of said gear chamber.

4. A portable belt sander as defined by claim 3 wherein the wall region has a recessed portion adapted to serve as a bearing retainer.

5. A portable belt sander as dened by claim 3 wherein the fan is supported by a separate shaft journaled in bearings in the suction unit.

6. In a portable belt sander. a sanding belt, a

pair of spaced rollers around which said belt is trained, a carriage comprising a plunger having at one end means in which one of said rollers is mounted, a cylinder in which said plunger is mounted for movement from an advanced, belt tightening position to a retracted, belt loosening position, a coil spring interposed between the plunger at its other end region and the end of said cylinder, for advancing the carriage, and a combined retracting and locking device comprising an element rotatably journaled in a wall of said cylinder, a plate secured to the cylinder wall, a shoulder on said rotatable element, said plate abutting said'shoulder and thereby holding the rotatable element in position in the cylinder wall, said element having an eccentric portion at one end engaged in a transverse notch in the adjacent side region of the plunger, and a lever secured to the other end of said rotatable element, adapted to engage the frame to limit its movement in belt loosening position, said eccentric portion being adapted to pass dead center of the line of pressure of said spring means, just prior to the reaching of the said limit of lever movement, so as to lock the carriage in its retracted belt loosening position. l ARTHUR WILLIAM MALL. 

